1. Field of the Invention
The present invention relates to methods for making soft magnetic alloys used in magnetic heads, transformers and choke coils.
2. Description of the Related Art
Soft magnetic alloys used in cores of magnetic heads, magnetic cores of pulse motors, transformers and choke coils generally require high saturation magnetic flux density, high permeability, low coercive force, formability into thin shapes, and low magnetostriction. Various alloys have been researched as soft magnetic materials satisfying such requirements.
Crystal alloys, such as Fe--Si--Al alloys (sendust alloys) and Fe--Si alloys (silicon steels), have been used in such soft magnetic applications. In addition, Fe- and Co-based amorphous alloys have recently been used.
Soft magnetic alloys are primarily used in the shape of a ribbon in various electronic instruments. A typical method for producing a soft magnetic alloy ribbon is a quenching process in which a melted alloy is injected or sprayed onto a cooling unit rotating at high speed to quench the alloy.
The soft magnetic alloy obtained by such a quenching process is substantially amorphous and annealed at a temperature higher than its crystallization temperature for approximately 1 hour to form a crystal phase in the amorphous phase, as disclosed in U.S. Pat. No. 4,881,989, in order to impart excellent magnetic characteristics, i.e., high saturation magnetic flux density and permeability, high hardness and excellent heat resistance to the soft magnetic alloy.
However, trends toward mass production of more compact high-performance instruments require methods for making soft magnetic alloys having superior magnetic characteristics, and in particular, higher permeability with higher productivity.